Add support for Java 15

Signed-off-by: Snjezana Peco <[email protected]>

README.md

@@ -20,7 +20,7 @@ Features
 =========
 ![ screencast ](https://raw.githubusercontent.com/redhat-developer/vscode-java/master/images/vscode-java.0.0.1.gif)
 
-* Supports code from Java 1.5 to Java 14
+* Supports code from Java 1.5 to Java 15
 * Maven pom.xml project support
 * Basic Gradle Java project support (Android not supported)
 * Standalone Java files support
@@ -77,6 +77,11 @@ If you need to compile your projects against a different JDK version, it's recom
     "path": "/path/to/jdk-14",
     "default": true
   },
+  {
+    "name": "JavaSE-15",
+    "path": "/path/to/jdk-15",
+    "default": true
+  },
 ]
 ```
 The default runtime will be used when you open standalone Java files.

package.json

@@ -494,7 +494,8 @@
                   "JavaSE-11",
                   "JavaSE-12",
                   "JavaSE-13",
-                  "JavaSE-14"
+                  "JavaSE-14",
+                  "JavaSE-15"
                 ],
                 "description": "Java Execution Environment name. Must be unique."
               },